Format: ORAL

Matin Miryeganeh, David W. Armitage

Okinawa Institute of Science and Technology Graduate University (OIST)

The tolerance adaptations of mangrove trees to osmotic stress, high temperatures, and low nutrients make them a promising model system for studying trees molecular responses to stress, which must occur relatively quickly to outpace climate change. Little is known about the transcriptomic and epigenomic contributions to stress responses and rapid local adaptation in mangroves. In Okinawa Japan, which near the global northern range limit of mangroves, we investigated the genomic, transcriptomic, and epigenetic contributions to stress adaptation over a local salinity gradient. Here, our data focuses on the mangrove Bruguiera gymnorhiza (Rhizophoraceae), which grows over a wide salinity but experiences stunted growth at the ocean. We focused on two patches of B. gymnorhiza growing within the same population but in two different saline environments one brackish (15 psu) and one oceanside (34 psu). Individuals within each patch display remarkable morphological and physiological differences which may be associated with the observed differential expression of stress responsive genes from transcriptomic analysis. In addition, trees in saline environments had genome-wide DNA hypermethylation, especially of transposable elements (TEs) indicating marked epigenetic structuring in the absence of population genetic differences.DNA hypermethylation was concurrent with the transcriptional regulation of chromatin modifier genes, suggesting robust epigenomic regulation of TEs in the mangrove genome under osmotic stress. We then performed a reciprocal transplant of mangrove propagules between sites to investigate if and for how long the trees remember their parental environmental conditions at the transcriptomic and epigenomic level.Following whole genome methylation and transcriptome analysis, our results provide evidence for the transient persistence of DNA methylation and gene expression pattern for several weeks after transplantation. These results provide a first glimpse into the mechanisms underlying wild trees adaptive capacities under novel stress conditions, which may be critical for understanding their responses to climate change more generally.